Free download · No email required

VPD chart, built to hang on a wall.

Twelve print-ready VPD charts in PDF — US Letter and A4, °F and °C, and a separate sheet for each leaf-temperature offset. Every cell prints its own value in kPa, the formula is on the sheet, and the whole thing still reads after you laminate it and run it through a photocopier.

  • 12 PDFs · 3 crop editions
  • °F and °C · US Letter and A4
  • 4 leaf-offset sheets · 0, −1, −2, −3 °C
  • kPa printed in every cell

Download the charts Use the VPD calculator

Printable AGEYE VPD chart — air temperature down the left, relative humidity across the top, leaf-level VPD in kPa in every cell, banded by growth stage, at a leaf-temperature offset of −2 °C
Cannabis & general edition, °F, leaf offset −2 °C. Every edition is drawn the same way.

Why this one

Everyone ships a widget. Nobody ships a sheet.

Leaf temperature, on purpose

Every VPD calculator has a leaf-offset box and none of them tells you what to put in it. These charts ship four sheets — one per offset — and a page explaining what to set and how to measure it. A chart drawn at air temperature overstates your VPD by roughly 0.2–0.5 kPa in a lit room.

The number is in the cell

No color-matching against a key in the corner. Every cell prints its own value in kPa to two decimals, so the chart answers the question directly and keeps answering it when the print fades or the room is dim.

Drawn for a printer, not a screen

Nothing thinner than 0.4 pt, no meaning resting on hue alone, and band boundaries drawn as heavy stepped rules. On a black-and-white photocopy the two danger bands go dark, the three working bands stay light, and the boundaries survive.

It shows its work

The Tetens equation is printed on every sheet, with a worked example on the reference page. It is the same equation behind the AGEYE VPD calculator, so the paper and the screen never disagree.

Download

Pick your crop, your units, your paper.

Each PDF is five pages: four wall charts at leaf offsets of 0, −1, −2 and −3 °C, then a reference sheet with the crop targets, the offset guidance and the math. Start with the −2 °C sheet if you have never measured your own offset.

Clone · Vegetative · Flower

VPD chart — Cannabis & general

The general-purpose sheet, banded on the 0.4 / 0.8 / 1.2 / 1.6 kPa spine most growers already work to: clones and seedlings, vegetative, flower, and the two zones you do not want to be in. Use it for cannabis, and for any crop whose targets you already know in kPa.

Growth-stage bands on the Cannabis & general VPD chart
VPD (kPa)Band
under 0.40 Too low — condensation and disease
0.40 – 0.79 Clones and seedlings
0.80 – 1.19 Vegetative
1.20 – 1.59 Flower
1.60 and up Stress — stomata close

62–88 °F / 17–30 °C · 30–90 % RH

°F US Letter PDF A4 PDF
°C US Letter PDF A4 PDF
VPD chart for cannabis & general — Clone · Vegetative · Flower, leaf-level VPD in kPa across air temperature and relative humidity

Tomato · Cucumber · Pepper · Strawberry

VPD chart — Greenhouse produce

Built around fruiting crops, which want — and tolerate — a higher deficit than leafy ones. A tomato crop held under 0.8 kPa through fruit set moves very little calcium, and that is where blossom-end rot starts. Runs cool enough at the top of the sheet to cover a greenhouse night temperature.

Growth-stage bands on the Greenhouse produce VPD chart
VPD (kPa)Band
under 0.40 Too low — guttation and botrytis
0.40 – 0.79 Transplant and establishment
0.80 – 1.19 Vegetative
1.20 – 1.59 Flower and fruit
1.60 and up Stress — abortion and blossom-end rot

58–84 °F / 15–28 °C · 30–90 % RH

°F US Letter PDF A4 PDF
°C US Letter PDF A4 PDF
VPD chart for greenhouse produce — Tomato · Cucumber · Pepper · Strawberry, leaf-level VPD in kPa across air temperature and relative humidity

Butterhead · Romaine · Arugula · Kale · Basil · Microgreens

VPD chart — Leafy greens & herbs

The edition nobody else publishes. Salad crops close out at 1.40 kPa, not the 1.60 kPa a generic chart shows you: lettuce cannot move calcium to a fast-growing leaf margin quickly enough above roughly 1.3 kPa, which is tipburn — a transpiration problem before it is a nutrient problem.

Growth-stage bands on the Leafy greens & herbs VPD chart
VPD (kPa)Band
under 0.40 Very low — germination only
0.40 – 0.79 Propagation
0.80 – 1.19 Grow-out
1.20 – 1.39 Finish and herbs
1.40 and up Too high — tipburn and bolting

58–84 °F / 15–28 °C · 30–90 % RH

°F US Letter PDF A4 PDF
°C US Letter PDF A4 PDF
VPD chart for leafy greens & herbs — Butterhead · Romaine · Arugula · Kale · Basil · Microgreens, leaf-level VPD in kPa across air temperature and relative humidity

The part nobody explains

Leaf temperature is what drives VPD.

A plant does not transpire against the air's temperature. Water evaporates from inside the leaf, so the pressure pushing it out is the saturation pressure at leaf temperature. The air only supplies the second half of the equation — how much vapor it is already carrying. Transpiration cools a leaf and light warms it, and under LED with real airflow the net is usually 1–3 °C below air.

What offset to set

SituationOffsetWhy
Lights off / dark period 0 to −0.5 °C No radiant load. The leaf sits at, or a little under, air temperature.
Low-intensity LED, gentle airflow −0.5 to −1.5 °C Modest transpiration; the leaf runs slightly cool.
Full-intensity LED, good airflow −1.5 to −2.5 °C The common case in a working indoor room. Start here.
High airflow, dry air, open canopy −2.5 to −3.5 °C Vigorous transpiration pulls leaf temperature well below air.
HPS / high radiant load −1.0 to +2.0 °C Radiant heat can push a leaf above air temperature. Measure, do not assume.
Water stress, closed stomata 0 to +3.0 °C A leaf that has stopped transpiring stops cooling itself.

Measure yours with an infrared thermometer set to emissivity 0.95: aim at a fully expanded, well-lit leaf from about 30 cm, slightly off perpendicular, average five leaves mid-photoperiod, and subtract air temperature at canopy height. Avoid the growing point and leaf edges — both run warm.

Which lever moves VPD fastest

ChangeVPD movesNote
Leaf offset, +1 °C +0.17 kPa The biggest lever on the page, and the one nobody measures.
Relative humidity, +5 pts −0.16 kPa Dehumidify or humidify — the fastest control you own.
Air temperature, +1 °C +0.06 kPa Roughly a third of the humidity lever. Weaker than it feels.

Measured at 25 °C, 60% RH and a −2 °C offset, from the same equation the charts are drawn with. Humidity is about three times the lever that air temperature is — and the leaf offset beats both. Getting the offset wrong is a larger error than reading humidity wrong by five points.

By crop

VPD targets by crop and growth stage.

Every range below is printed on the reference sheet of the edition it belongs to, and banded directly into that edition's grid.

VPD chart for lettuce

Butterhead, romaine, leaf

Target VPD for Lettuce by growth stage, in kPa
StageTarget VPD (kPa)
Propagation0.4 – 0.8
Grow-out0.8 – 1.2
Pre-harvest1.0 – 1.3

Lettuce works at 0.8–1.2 kPa through grow-out and should not be pushed past about 1.3 kPa. Above that the leaf margin outgrows the plant's ability to deliver calcium to it, and you get tipburn — which is why raising VPD to dry a wet room so often produces burnt edges a week later. Drop toward the bottom of the band in the last days before harvest to keep the head turgid.

Download the leafy greens & herbs chart →

VPD chart for tomatoes

Greenhouse and indoor

Target VPD for Tomatoes by growth stage, in kPa
StageTarget VPD (kPa)
Transplant0.4 – 0.8
Vegetative0.9 – 1.3
Flower1.0 – 1.5
Fruit1.2 – 1.6

Tomatoes are one of the few crops where a higher deficit is the goal rather than the risk. Transpiration is what carries calcium into fruit, so a crop held below 0.8 kPa through fruit set is quietly setting up blossom-end rot. Keep the vegetative phase near 1.0–1.2 kPa, then let fruiting sit at 1.2–1.5. Night VPD matters too: a cold, saturated house condenses on the fruit.

Download the greenhouse produce chart →

VPD chart for strawberries

Everbearing and June-bearing

Target VPD for Strawberries by growth stage, in kPa
StageTarget VPD (kPa)
Establishment0.5 – 0.9
Flower0.9 – 1.3
Fruit1.0 – 1.5

Strawberries are the crop where low VPD costs you the most, and it is not a growth problem — it is botrytis. Open flowers sitting in near-saturated air are the single highest-risk moment in the crop. Hold flowering at 0.9–1.3 kPa and keep air moving through the canopy; if you have to choose, take the drier end during bloom and the wetter end during establishment.

Download the greenhouse produce chart →

VPD chart for peppers

Bell and specialty

Target VPD for Peppers by growth stage, in kPa
StageTarget VPD (kPa)
Transplant0.4 – 0.8
Vegetative0.9 – 1.3
Flower1.0 – 1.5
Fruit1.2 – 1.6

Peppers track tomatoes closely, with one difference that matters: flower abortion. Pushing past about 1.6 kPa while flowers are open costs fruit set outright, and no amount of feeding gets it back. Peppers also carry less leaf area than a tomato crop, so they cool themselves less — expect a smaller leaf-temperature offset and check it rather than assuming the tomato number carries over.

Download the greenhouse produce chart →

VPD chart for cucumbers

Long English and mini

Target VPD for Cucumbers by growth stage, in kPa
StageTarget VPD (kPa)
Transplant0.4 – 0.8
Vegetative0.8 – 1.2
Fruit1.0 – 1.5

Cucumbers run a full band lower than tomatoes because they carry enormous leaf area and transpire hard. That same leaf area makes their leaf-temperature offset the largest of any greenhouse crop — often 2.5–3 °C below air under full light — so a chart drawn at air temperature will tell you the house is far drier than the plant thinks it is. Use the −2 or −3 °C sheet.

Download the greenhouse produce chart →

VPD chart for basil

Genovese and specialty

Target VPD for Basil by growth stage, in kPa
StageTarget VPD (kPa)
Propagation0.4 – 0.8
Vegetative0.9 – 1.3
Harvest1.0 – 1.4

Basil is the one leafy crop that wants a drier room than lettuce, and it is the reason the leafy-greens sheet runs to 1.40 kPa rather than stopping at 1.20. It is also the crop that punishes a wet room fastest: downy mildew establishes in still, saturated air, so if basil and lettuce share a room, set the environment for basil and accept the lettuce is at the top of its band.

Download the leafy greens & herbs chart →

VPD chart for kale

Baby leaf and full size

Target VPD for Kale by growth stage, in kPa
StageTarget VPD (kPa)
Propagation0.4 – 0.8
Grow-out0.8 – 1.2
Harvest1.0 – 1.3

Kale sits where lettuce sits and is considerably more forgiving at the top of the band — the waxy cuticle slows water loss enough that a brief excursion past 1.3 kPa does not show up as tipburn the way it does in butterhead. Treat that tolerance as headroom, not a target: growth still stalls once stomata start closing.

Download the leafy greens & herbs chart →

VPD chart for arugula

Baby leaf

Target VPD for Arugula by growth stage, in kPa
StageTarget VPD (kPa)
Propagation0.4 – 0.8
Grow-out0.8 – 1.1
Harvest0.9 – 1.2

Arugula has the narrowest usable window of any crop on these sheets — 0.8–1.1 kPa through grow-out. Thin leaves and a fast cycle mean it responds to a drifting environment within a day, and the response is bolting and a harsher, more bitter leaf rather than a visible defect. If one crop justifies watching leaf temperature rather than air, it is this one.

Download the leafy greens & herbs chart →

VPD chart for microgreens

Germination through harvest

Target VPD for Microgreens by growth stage, in kPa
StageTarget VPD (kPa)
Germination0.2 – 0.5
Greening0.5 – 0.9
Harvest0.6 – 1.0

Microgreens are the exception on the whole chart: germination wants a VPD low enough that every other crop on these sheets would call it a disease risk. That is what a blackout dome is for. The transition out of the dome is the moment to watch — going from 0.2 kPa to 0.9 kPa in one step wilts a stand of seedlings that has no root system to draw on yet.

Download the leafy greens & herbs chart →

VPD chart for cannabis

Clone through late flower

Target VPD for Cannabis by growth stage, in kPa
StageTarget VPD (kPa)
Clone / seedling0.4 – 0.8
Early veg0.8 – 1.0
Late veg1.0 – 1.2
Early flower1.2 – 1.4
Late flower1.4 – 1.6

The cannabis progression is a steady ramp rather than a set point: low and humid for un-rooted clones, then up through veg, then drier through flower to tighten flower structure and keep botrytis out of dense colas. Cannabis also runs some of the largest leaf-temperature offsets in the industry, because grow rooms combine high light intensity with heavy airflow.

Download the cannabis & general chart →

How to read it

Four steps, then it is a wall chart.

  1. 1Measure air temperature and relative humidity at the canopy, not at the controller.
  2. 2Pick the sheet whose leaf-temperature offset matches your room. If you have never measured yours, use the −2 °C sheet.
  3. 3Find your temperature down the left edge and your humidity across the top. The number where they meet is your leaf-level VPD in kPa.
  4. 4Compare that number against the band your crop is in right now — the band legend at the foot of every sheet names them.

The math

Tetens, and nothing hidden.

VPD    = es(T_leaf) − (RH/100) × es(T_air)
es(T)  = 0.6108 × exp( (17.27 × T) / (T + 237.3) )
T_leaf = T_air + offset

T is temperature in °C and es is saturation vapor pressure in kPa. Fahrenheit is converted to Celsius before the equation is applied, never after.

Worked example. Air 25.0 °C (77.0 °F), RH 60%, offset −2 °C. The leaf is at 23.0 °C. es(23.0) = 2.8094 kPa and es(25.0) = 3.1678 kPa, so VPD = 2.8094 − 0.60 × 3.1678 = 0.91 kPa. That cell is in the vegetative band.

Straight answers

Questions growers actually ask

Is there a VPD chart PDF I can print?
Yes. This page has twelve of them, free and without an email wall: three crop editions (cannabis and general, greenhouse produce, leafy greens and herbs), each in Fahrenheit and Celsius, each for US Letter and A4. Every PDF is five pages — four wall charts, one per leaf-temperature offset, plus a reference sheet covering the crop targets, how to measure leaf temperature, and the equation.
What size should I print a VPD chart at?
Portrait, at 100% or "Actual Size" — never "Fit to Page", which shrinks the grid and the type with it. Download the US Letter edition for US Letter paper and the A4 edition for A4; they are drawn separately rather than scaled, so each one keeps full contrast at the band edges. Laminating is expected, and the sheets are drawn to survive a black-and-white photocopy of a laminated copy.
Is there a VPD chart in Celsius?
Yes. Every edition ships in both °C and °F, and each sheet also prints the other unit in small type down the temperature axis, so a farm running mixed instruments can read one chart. VPD itself is in kilopascals (kPa) throughout.
What is the leaf temperature offset on a VPD chart?
It is how far below air temperature the leaf actually sits. It matters because a plant does not transpire against the air's temperature: water evaporates from inside the leaf, so the pressure driving it out is the saturation pressure at LEAF temperature. Air only supplies the second half of the equation, the vapor it is already carrying. Transpiration cools a leaf and light warms it; under LED with real airflow the net is usually 1–3 °C below air.
What leaf temperature offset should I use?
Start at −2 °C for a room under full-intensity LED with good airflow, which is why that is the sheet marked "start here" in every pack. Use 0 for lights-off, −1 for low-intensity light or gentle airflow, and −3 for dry air, high airflow and an open canopy. Under HPS or any high radiant load the leaf can run warmer than the air, so measure rather than assume. At 25 °C and 60% RH, each 1 °C of offset moves VPD by about 0.18 kPa — a bigger error than reading humidity wrong by five points.
How do I measure my own leaf temperature offset?
Use an infrared thermometer set to emissivity 0.95. Aim at a fully expanded, well-lit leaf from about 30 cm, slightly off perpendicular so you are not reading your own reflection. Average five leaves across the zone, mid-photoperiod, and subtract air temperature measured at canopy height. Avoid the growing point and leaf edges, which both run warm, and re-measure whenever you change light intensity, airflow or crop stage.
What VPD should I use for lettuce?
Around 0.8–1.2 kPa through grow-out, 0.4–0.8 kPa in propagation, and no higher than about 1.3 kPa before harvest. Lettuce cannot deliver calcium to a fast-growing leaf margin quickly enough above roughly 1.3 kPa, which is what tipburn is. That is why the leafy greens edition of this chart closes out at 1.40 kPa rather than the 1.60 kPa a generic chart shows.
What VPD should I use for tomatoes?
0.9–1.3 kPa in the vegetative phase and 1.2–1.6 kPa through fruiting, with transplants held at 0.4–0.8 kPa. Fruiting crops want the higher deficit: transpiration is what carries calcium into the fruit, so a tomato crop kept under 0.8 kPa through fruit set is setting up blossom-end rot even when everything in the feed is correct.
How is VPD calculated on these charts?
VPD = es(T_leaf) − (RH/100) × es(T_air), where es is saturation vapor pressure from the Tetens equation: es(T) = 0.6108 × exp((17.27 × T) / (T + 237.3)), with T in °C and es in kPa. Fahrenheit values are converted to Celsius before the equation is applied, never after. It is the same equation the AGEYE VPD calculator runs, so the chart and the calculator always agree.
Why does my chart say "dew" instead of a number?
Because at that combination the leaf is at or below the dew point, and water is condensing on it. The deficit there is not a small number, it is zero with liquid water on the leaf surface — printing "0.00" would read like a rounding artifact and hide the one condition on the chart that can ruin a crop overnight. Those cells appear at high humidity on the larger leaf-offset sheets, which is exactly when a cool leaf in a wet room starts collecting water.
Do I have to give my email to download the VPD chart?
No. There is no form, no sign-up and no tracking pixel on the download. Every PDF on this page is a direct link, free to print, post, photocopy and share.

The chart tells you where you are. Sensors tell you where you have been.

A laminated sheet answers one reading at one moment. AGEYE measures temperature, humidity, VPD and light continuously in every zone, and flags drift before it becomes a crop problem — the difference between a targeted fix and a facility-wide one.

Talk to us about monitoring

Questions about the charts? hello@ageyetech.com